The Western Black Rhino has been declared extinct. On November 10, 2011 the International Union for the Conservation of Nature made the official declaration.
The Western Black Rhino is the subspecies that once lived in the savanna belt of the Cameroons; it is separated by several thousand miles from the surviving Black Rhinos of southern and eastern Africa. All sorts of statistical issues surround its extinction.
How long has it been gone? An intensive survey in 2006 across its former ranges in Cameroon failed to find any. It is just possible that a small population in an inaccessible area had been missed, but if so you would have expected it to have emerged and been spotted by now – and the longer the wait, the less likely such a survival becomes. See this article for how long you would expect to wait without seeing an animal before you can confidently say that there are none of them left.
A rhino, you would have thought, would be relatively easy to spot if in fact there is one there; but one of the great debates in elephant conservation is over how many elephants there actually are – and it is surprisingly difficult to say. You would have thought that the biggest of all land animals would be easy to count – but how can you tell them apart and be sure that you haven’t counted the same one twice? Forest elephants cannot be see from the air; the way that you estimate their numbers is by looking for their dung and doing a statistical sum involving how hard you look, what proportion of the total number of elephant dunghills you are likely to spot, and, I suppose, how many times a day an elephant relieves itself. The result will, of course, have a lot of uncertainty in it.
A major contributor to the Western Black Rhino’s extinction, and to the precarious condition of the other rhino sub-species, is demand for their horn – as a supposed aphrodisiac in Asia, and as prized handles for ornamental daggers in the Middle East. A major driver for elephant poaching is demand for ivory. Trading in non-antique ivory is currently illegal or highly restricted. There has been an impassioned debate among conservationists: several counties have quite large stocks of ivory that has been confiscated from poachers. Would releasing this ivory onto the market signal that ivory is indeed saleable, and so give poachers a green light? Or would it have no effect on poaching at all? Again, the only way to find out is by statistically examining estimates of elephant poaching before and after an agreed sale; for more on these issues see this article, elephants and ivory, by Bob Burns, in Significance 4.3
A similar situation exists for whales. The International Whaling Commission (IWC) sees an annual battle between those nations who want to keep a ban on commercial whaling and those, like Japan, who seek to continue killing whales and obtaining whale-meat under the banner of ‘scientific research.’ How do you count the number of whales that remain? And how do you decide between the two sides? The issue is an emotional one – there is probably no common ground to be found between those who see whales as warm-blooded intelligent close relatives whom it is morally indefensible to kill and those who see them simply as profitable protein; but it is also an extremely practical one – see this article by a former chairman of the scientific committee of the IWC. There are many different species of whale, and they exist in vastly differing numbers. There are, for example, perhaps as many as a million Minke whales in the oceans; in recent years about a thousand have been killed annually by countries such as Norway and Japan; this is unlikely to affect the species survival. But in the early days of whaling blue whales were as relatively common in the oceans as Black Rhino once were in their habitat; probably no more than a few thousand now remain. For this species, it is possible that it is already too late, and the Blue Whale may already in essence have joined the Western Black Rhino.